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Lipid bilayers: barrier for the entry of drugs into cells by passive diffusion

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Ambiguous amphiphiles In order to be useful as a drug a compound has to dissolve in water  hydrophilicity required has to permeate lipid bilayers  lipophilicity required Hydrophilic part e.g. carboxylic acid derivatives Lipophilic part e.g. hydrocarbon chain

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Air-water interface – a good model for lipid membranes Amphiphiles are strongly oriented in lipid membranes and in the air-water interface. Partitioning into both interfaces is mainly driven by the hydrophobic effect Air/water interface:Phospholipid bilayer: